Old Rocks in Greenland
Credit: AAAS
They might not look like much, but these weathered rocks have been chilling for a long time along the east coast of Greenland. Scientists believe they may be the oldest chunk of the Earth’s crust ever found.
“An international team has found a sequence of rocks in Greenland that formed as the sea floor split apart 3.8 billion years ago, a discovery that helps define when the Earth’s plate tectonics system kicked into gear,” according to a release from the journal of Science.
The Earth’s crust is continually being formed at spreading ridges in the middle of the oceans, where plates roll apart, and above subduction zones, where material from the sinking plate can get scraped off onto the edge of the stationary plate. Scientists have debated whether plate tectonics occurred early in Earth’s history or just in the latter half of its 4.5 billion-year existence. The old age of the Greenland rocks suggests that the plate tectonics system arose relatively early.
Led by geochemist Harald Furnes at the University of Bergen in Norway, , the team of five scientists analyzed a belt of twisted, deformed rocks in southwestern Greenland. The rocks turned out to be examples of ophiolites, originally formed on the ocean floor when tectonic plates spread apart. The ophiolites — which means “snake stone” in Greek — then gets uplifted to the surface over eons.
Furnes has long investigated ancient rocks for clues to the early Earth. In 2004, Furnes and his team reported finding burrows left by worms some 3.5 billion years ago.